1. Field of the Invention
The present invention relates to an air cleaner for removing house dust and an air cleaner with a sterilization function to remove bacteria and virus from air in a room.
2. Related Art
Recently, it has been reported that one-third or one-fourth of Japanese people have an allergy. Thus, it is desired to remove house dust which is disadvantageous for persons having an allergy.
The house dust consists of minute particles floating ina room. The house dust includes those derived from mites (acarid), fine fibers, food drops, and pollen or spore of a plant. Tobacco smoke is also included in the house dust.
The airborne infection (including droplet infection) of bacteria, viruses, and the like is caused by coughs and sneezing of sick persons or carriers. Recently, it has been a social problem that a mass infection appears in a hospital, an old-aged home, and a physical care house particularly due to pathogenic microbes. The microbes include phthisis germs, derived from a carrier thereof and Legionella germs contained in droplets of a cooling water of an air-conditioner.
One of such air cleaners for removing house dust, bacteria, and virus is an electrical-discharge-type air cleaner having a minus ion generator. FIG. 5 shows an example of the air cleaner.
To provide a minus ion generator, an aerial conductive wire carrying a high minus voltage is developed, and a non-woven fabric is arranged near the wire. The non-woven fabric is grounded through a ground pole or carries a high plus voltage through a positive pole.
The house dust and bacteria which are floating in air are charged by minus ions when they come close to the wire, so that the non-woven fabric catches them. Then, the non-woven fabric which has caught the house dust and bacteria is adequately replaced by a new one.
Note that the air cleaner is generally received in an air-permeable housing to protect the wire.
However, the electrical-discharge-type air cleaner generates ultraviolet rays due to the electric discharge between the minus ion generator and the positive/ground pole, which generates ozone. Thus, the air cleaner has a disadvantage that is the same as an ultraviolet-ray-type bactericidal lamp and an ozone generator. Moreover, it is generally overlooked that the electrical-discharge-type air cleaner generates ozone and ultraviolet rays which are harmful. Such air cleaners have been often positioned undesirably near a sleeping baby for supplying clean air.
The conventional air cleaner takes a long time until it effectively operates. For example, The time is 30 minutes to one hour for a room having a general size. Thus, persons in the room remain exposed to house dust, bacteria, and viruses, for example, due to smoking, airborne dust, and a cough of a sick person having viruses until the air cleaner operates effectively.
Another air cleaner removing house dust by a filter takes a time between 30 minutes and one hour until it operates effectively. The filter should be a specially designed one which is expensive for removing house dust consisting of particles of micron or sub-micron sizes such as tobacco smoke, bacteria, and virus. Moreover, such a filter provides a combatively larger pressure loss and requires a powerful fan, which causes an increased electrical energy and a noise problem. In addition, the filter has a shorter service life to require frequent replacements thereof. Furthermore, the filter-type air cleaner has the disadvantage that a bactericidal means is not effectively provided for sterilization of the bacteria which is caught by the filter.
For sterilization of airborne bacteria, there may be provided a means such as an ultraviolet-ray-type bactericidal lamp, an ozone generator, or an agent spraying device. An appropriate concentration of ozone generated by the bactericidal lamp is 0.1 PPM, for example in an office. However, the ozone having this concentration still irritates a mucosa of a nose, an eye, or a throat. Furthermore, the ozone provides an odor undesirable for a surrounding air. To remove the undesirable odor, an activated carbon filter is required. The ozone may cause a harmful NOx.
Meanwhile, the bactericidal lamp irradiates ultraviolet rays directly into a human body with an adverse effect. Even ultraviolet rays having a wavelength of around 260 nanometers which provides a maximum bactericidal effect require several hours to kill bacteria such as colibacillus. This is disadvantageous for a quick sterilization. In addition, the ultraviolet ray degrades a metal, a rubber, and a plastic product, and it also generates harmful ozone. An agent is not adequately sprayed in an environment in which persons are always present, and the effectiveness of the agent will not reliably continue.
In view of the above-mentioned disadvantages, an object of the invention is to provide an air cleaner and an air cleaning method according to the present invention, which allows an effective, quick air cleaning and air sterilization with no use of ozone, ultraviolet ray, and agents which are harmful and uncomfortable for persons.
For achieving the object, an air cleaner of a first aspect of the present invention includes a minus ion generator and a positive electrode. The minus ion generator uses a high minus voltage, and the positive electrode carries a high plus voltage. The minus ion generator can be positioned apart from the plus ion electrode, allowing an effective, quick air cleaning for a desired space.
Preferably, the minus ion generator has a heater, which generates effectively minus ions, allowing a quicker air cleaning.
Preferably, the positive electrode carrying the high plus voltage is positioned close to an absorbing sheet, which can effectively collect house dust which comes around the positive electrode.
An air cleaning method includes a minus ion generator and a positive electrode. The minus iongenerator carries a highminus voltage, and the positive electrode carries a high plus voltage. The method includes arrangement of the minus ion generator and the positive electrode which are positioned in a room for air-cleaning of the room. The minus ion generator is apart from the positive electrode by a distance not less than a half of the maximum distance between walls of the room. This allows a quick, effective air cleaning.
Note that the effect of the present invention may be decreased when there is provided a distance not enough for the quick air cleaning between the minus ion generator and the positive electrode.
Another air cleaner with a sterilizing function according to the present invention includes a minus ion generator and a positive electrode. The minus ion generator carries a high minus voltage, and the positive electrode carries a high plus voltage. The minus ion generator is separately positioned from the positive electrode. In a desired room, the minus ion generator is spaced from the positive electrode, allowing a quick, effective air cleaning.
Examples of the present invention will be discussed hereinafter. An air cleaner has a minus ion generator and a positive electrode which are arranged independently from each other. The minus ion generator carries a high minus voltage, and the positive electrode carries a high plus voltage. The minus ion generator is positioned apart from the positive electrode by a distance not less than a half of the maximum distance between walls of a room. This allows a quick, effective air cleaning and air sterilization.
For embodying the present invention, the minus ion generator and the positive electrode are positioned apart from each other by a distance which prevents an electrical discharge between them. An electrical discharge occurred between them generates ozone and ultraviolet rays. This requires an undesirable increased electrical power and obtains no effect of the present invention. The air cleaner according to the present invention is of an air condenser type consisting of the minus ion generator, the positive electrode, and air sandwiched therebetween. In the present invention, a ground voltage is a base (zero Volt) of the pole voltage. The ground voltage may be an earth voltage or may be a ground voltage of the room in which the air cleaner is disposed.
Preferably, the positive electrode carrying the high plus voltage is positioned close to an absorbing sheet having a comparatively broad surface. The absorbing sheet may be a needle punched fabric, a non-woven fabric, a woven fabric, or a knitted work. The absorbing sheet can catch the house dust and floating bacteria and viruses (which are called as the house dust hereinafter) effectively. Because, the house dust witch minus ions is drawn in the positive electrode side. The house dust can be easily sterilized. The catching and sterilizing operations are quick and reliable. The absorbing sheet having no electrical conductivity can provide a sufficient effect. Preferably, the absorbing sheet has an electrical conductivity so that the whole of the face of the absorbing sheet is effective for catching the house dust, allowing a quicker cleaning operation.
In addition, the absorbing sheet may be provided with or incorporated with a substance having a large service surface area for deodorizing air of the room at the same time. The substance is an activated carbon (including an activated carbon fabric and a fabric activated carbon), a silica gel, a zeolite, etc.
The absorbing sheet is required to be adequately replaced by a new one. Preferably, a rolled absorbing sheet fed by a drive roll may be used to intermittently provide anew part thereof when a part of the sheet has sufficiently absorbed the house dust. This greatly eliminates a large amount of manual works for replacement of the absorbing sheets. A timer may be provided to intermittently feed a length of the sheet every predetermined time. Alternatively, A stepping motor or a low speed motor may be provided to continuously feed the sheet.
Preferably, the absorbing sheet has initially a white or a bright color. The absorbing sheet becomes a dark color such as a dark brown or a gray when the sheet has caught the house dust. A roll motor is controlled to most adequately feed the sheet by sensing a light reflectance or transmittance rate of the sheet to know a changed color grade of the sheet.
The minus ion generator may have such a shape as a plate, straight wires, a net, a basket, or a honeycomb structure, as far as it is a striped electrode carrying a high minus voltage. Preferably, the electrode has a maximum area facing air and has a shape with a small pressure loss coefficient for an air flow, so that the electrode provides minus ions to the airborne house dust. Similarly, the positive electrode may have such a shape as a plate, straight wires, a net, a basket, or a honeycomb structure.
In the present invention, the minus ion generator carries a high minus voltage relative to a ground voltage, while the positive electrode carries a plus high voltage relative to the ground voltage. To prevent danger or to prevent the entry of large particles of dust, the air cleaner preferably has a housing provided with a protect means having air-permeability such as a net or an entrance consisting of slits. The housing may have a filter to prevent the entry of the large dust particles.
Preferably, the minus ion generator is provided with a heater. The heater heats air around it, for example to temperatures between 30xc2x0 C. and 80xc2x0 C. The heated air is supplied to the minus ion generator, which enables a more effective operation of the minus ionization of the house dust and the sterilization.
The minus ion generator may have an air feed means like a fan so that the house dust having the minus ions can be quickly delivered to the positive electrode side. In place of the air feed means, the heater may be positioned under the minus ion generator, or the minus ion generator may be located an air out let of an air conditioner or a vent means to maintain the same effect of the air feed means.
The air feed means may be a small fan with a smaller air feeding capacity or may be a larger one with a low rotating speed, allowing a quiet operation and a small electrical energy of the air feed means. This provides an advantage over a conventional filter-type air cleaner. That is because the minus ion generator itself has a shape with an air pressure loss coefficient, which is, for example, constituted by a large-mesh wire net or a plurality of short metal cylinders defining a honeycomb structure.
The minus ion generator and the positive electrode may be increased in number according to the shape and size of the room. Note that the minus ion generator is spaced as far as possible from the positive electrode to allow an effective removal and sterilization of the house dust.
The application voltages of the minus ion generator and the positive electrode are selected so as not to produce an electrical discharge therebetween and not to produce an electrical breakdown of a retainer of the minus ion generator.
Actually, it has been found to allow an effective removal and sterilization of the house dust that the absolute value of an application voltage of the minus ion generator is not less than the absolute value of an application voltage of the positive electrode. Furthermore, it has been found that a higher application voltage of the positive electrode produces a larger electrostatic charge in the room. The larger electrostatic charge makes persons in the room more uncomfortable due to an electrical discharge when they touch a metal like a door knob.
A minus voltage power source is provided to keep the high minus voltage of the minus ion generator, while a plus voltage power source is provided to keep the high plus voltage of the positive electrode. The power sources may be those used in a conventional air cleaner.
Note that the application voltages need not be constant but may have a small fluctuation to achieve a more effective operation of the air cleaning and bacteria removal. Such a fluctuating high voltage application is enabled by a timer circuit and a switching circuit.